1. Field of the Invention
The present invention relates to a junction element for connecting wirings used in an electronic apparatus such as a magnetic disc apparatus, an optical disc apparatus or a magneto-optical disc apparatus and, in particular, to a substrate junction element capable of reliably connecting substrates differing in thickness.
2. Description of the Related Art
FIG. 5 is a partial perspective view showing a wiring junction process for a magnetic head device provided in a conventional floppy disk apparatus, and FIG. 6 is a partial perspective view showing the construction after the connection of the wiring.
In a magnetic head device for a floppy disk apparatus, magnetic heads are symmetrically opposed to each other with the disk serving as the magnetic medium being therebetween. The magnetic head positioned above the disk is supported by a gimbal, and the magnetic head positioned below the disk is supported by a plate.
Each magnetic head is connected to a wiring substrate, which extends over a carriage 1 positioned at the rear end of the magnetic head device.
In FIG. 5, numeral 2 indicates the wiring substrate connected to the magnetic head positioned below the disk, and numeral 3 indicates the wiring substrate connected to the magnetic head positioned above the disk. On the wiring substrates 2 and 3, conductive leads connected to electrode portions of the magnetic heads are formed, and these conductive leads are connected to connection land portions 2a and 3a at the rear end of the wiring substrates 2 and 3. Further, as shown in FIG. 5, the wiring substrates 2 and 3 have holes 2b and 3b formed in the vicinity of the connection land portions 2a and 3a.
Further, a main substrate 4 is installed on the carriage 1. This main substrate 4 comprises a thin-film substrate 5 on which predetermined electronic parts constituting recording/reproduction circuits, etc. are mounted, and a reinforcing plate 6 joined to the back side thereof and having a fixed thickness. Formed on the thin-film substrate 5 is a conductive lead connected to the electrode portions of the electronic parts, and a part of the conductive lead extends to the forward end of the thin-film substrate 5 and is connected to connection land portions 5a.
As shown in FIG. 5, a protrusion 1a is formed on the carriage 1, and the protrusion 1a is passed through a hole 4a formed in the main substrate 4, whereby the positioning of the main substrate 4 on the carriage 1 is effected.
Further, the protrusion la is passed through the holes 2b and 3b formed in the wiring substrates 2 and 3, which are placed on the main substrate 4, whereby the connection land portions 2a and 3a of the wiring substrates 2 and 3 are partly superimposed on the connection land portion 5a of the main substrate 4.
Then, as shown in FIG. 6. the connection land portions 2a and 3a of the upwardly exposed wiring substrates 2 and 3 and the connection land portion 5a of the main substrate 4 are soldered (shaded portion) to thereby effect conductive connection.
However, in the construction in which the main substrate 4 is arranged on the carriage 1 and then the wiring substrates 2 and 3 are placed thereon to solder the connection land portions 2a and 3a of the wiring substrates 2 and 3 to the connection land portions 5a of the main substrate 4, the connection land portions 2a and 3a are apt to rise from the connection land portions 5a of the main substrate 4 due to warpage, etc. of the wiring substrates 2 and 3.
Thus, it is necessary to solder the connection land portions 2a and 3a to the connection land portions 5a while pressing the wiring substrates 2 and 3 to the surface of the main substrate 4 by using a tool such as a pair of tweezers, with the result that the soldering operation is very difficult. Further, when the wiring substrates 2 and 3 rise during or immediately after the soldering operation, the solder between the connection land portions is broken or separated, with the result that defective soldering,.is likely to occur.